Seismic signal display system



July 6, 1965 R. w. MITCHELL. JR

SEISMIC SIGNAL DISPLAY SYSTEM Filed March 5, 1962 2 Sheets-Sheet 1 IIIIIIJ :Eirow rlmmm n p Amp. N w

Qu w l om fwn mun-41m ROSCOE W. MITCHELL, JRJNVENTOR.

BY Q

ATTORNEY Tlw.

July 6, 1955 R. w. MITCHELL. JR 3,193,838

smsmc SIGNAL DISPLAY sYsTEM Filed March 5, 1962 2 sheets-Sheet z t 1 1" I l L J F I I l J- l N l L l 3 FIG. 2

84 RED BLUE GREEN ROSCOE W. MITCHELL, JR. INVENTOR.

FIG. 3

ATTORNEY..

3,193,335 SEISMlC SEGNAL DlSPLAY SYSTEM Roscoe W. Mitchell, Er., Tulsa, Okla., assigner, by mesne assignments, to Esso Production Research Company,

Houston, Tex., a corporation of Delaware Filed Mar. 5, 1962, Ser. No. t'' 7 Claims. (Cl. Sen-lill) This invention concerns the display` of signals having amplitude variations with respect to time. lt relates especially to the display in color of information contained in a seismic signal. v

Geophysical prospecting using artificially induced seismic disturbances has found wide application in the search for petroleum and other products. t is the general practice to initiate a seismic disturbance at a point near the surface of the earth to direct seismic waves downward into the earth from thatv point. The waves continue to travel downward within the earth until they encounter discontinuities in the `earths structure in the form of various substrate formations and the like. These discontinuities have the elect of reflecting at least a portion of the seismic waves back toward the surface of the earth. By arranging a plurality of, geophones or other seismic transducers at spaced distances from the seismic disturbance point, it is possible to detect the arrival of the reflected seismic waves at the surface of the earth. These detected waves are translated into electrical impulses which are then indicative of the character of the ground motion and are usually referred to collectively as a seismic signal. The seismic signal is in eiect a composite signalrnade up of a plurality of electrical signals varying in frequency and amplitude.

One technique that has recently been found useful in the processing of a seismic signal is the display of certain characteristics or the signal in color. A specic technique that has recently vbeen useful in the processing of seismic data is the frequency analysis display. In this specilic system a time interval between successive signiiicant features, such as Zero crossings of the seismic signal, is measured. The time interval measurement is converted to a voltage proportional to the time. The voltage is then used to deect a mirror galvanometer. A color wedge is spaced between the mirror galvanometer and a recording medium. A light beam is reflected from the mirror galvanometer through the color wedge onto the recording medium. rl`his results in a color representation on, the recording Vmedium of the particular frequency for each half cycle of the original seismic signal. While this system has proved to be quite benelicial, it is not without its diiliculty. Among the problems are diliiculty in aligning the galvanometers, diliculty in duplicating color filter wedges so `that the results obtained from two diierent wedges can be duplicated. ,There is also a resultant heat dissipation problem resulting from the use of a lamp kpowerful enough to provide suthcient light for use with the color wedges.

This invention overcomes "or reduces, all of these" problems.` Y

Briefly, the present invention broadly includes a system for presenting or displaying a signal which has amplitude variationsrwith respect to time. The face of a cathode ray tube is provided with three distinct bands of phosphorescent material, each band being ot'a character to emit a separate-primary color when energized by the electronbeam of the cathode ray tube. Means are provided to sweep traversely the electron beam across each band sequentially.l The intensity of the electron beam during each sweep is a function ot the signal being processed. Optical means areY provided to display the beam of light received from the cathode ray tube as a single nited States Patent() l Patented July, 1965 ICE Vin circuit forni, the best mode contemplated for carrying out this invention;

FIG. 2 illustrates the waveforms at various points of the embodiment of FlG. 1; and,

FEG. 3 illustrates the face of the cathode ray tube and the path of the electron beam thereon.

illustrated on FIG. l is input signal source lll and sweep generator l2. lnput signal l@ can take on various forms but in general is said to have amplitude variations which vary from time to time. One such signal is schematically illustrated ,as curve H of FIG. 2. The amplitude of the level and its duration can, for example, represent the time between successive zero crossings of the seismic signais; that is, the distance between twosuccessive points where the seismic signal crosses a zero reference base line. A particularly suitable means for obtaining a curve such as H is shown in U.S`. patent application Serial No. S3l,248 filed August 3, 1959 now Patent No. 3,063,014 in the name of .lohn L. Shanks. t is to be understood that this invention is not limited to the waveform represented by curve H of FlG. 2, but can be used for essentiallyv any signal having amplitude variations.

A sweep generator 12. is provided and has an output such as sawtooth waveform A of PEG. 2. The frequency of the sau/tooth waveform should be several times greater, i.e.V at least ten ormore, than the highest ireojlency of the input signal H. A typical value for this sawtooth frequency is 2G00 cycles per second when processing a typical seismic signal. The output from sawto'oth generator l2 is fed to a trigger pulse Shaper lli which develops or has an output of synchronizing trigger'v pulses coincident with the retrace of the sweep waveform. Such an output is illustrated as waveform B in FlG. 2. The output of trigger pulse shaper i4 is fed toa ring counter. 16. i l

Ring counter lo includes three lai-stable multivibrators or tlipilops l, Ztl and 22. Gate circuits 24, 26and 28 are used in conjunction with the three. flip-flops 18, 20

and 221. The gate circuits 24, 26 and 2S are illustrated as being the type commonly known as and gates. Ari output level other than zero is present if, and only if,'a voltage level is present on all inputs to an and gate. A voltage level applied to one or moreinputs, so that a pulsecan pass through, are said to enable the gate.

- 22a and ZZb from which waveforms E and F respectively or FG. 2 Vare taken. The output F is an inverted form of output E, i.e., when a voltage exists at E, then no voltage is present at F, and when no voltage is present at E, a voltage is present at F. The output F of multi- Vibrator 22 and the output C of multivibrator i8 are fed through blocking capacitors 36 and 3S and isolating re- Y The signal j sisters Si? and 32 to a junction point 34. developed across resistor 37 and obtained at 34 is a stairstep.l waveform illustrated in curve G of FIG. 2. lt Vwill Vv/aveforrn G is connected to amplifier il? which drives adsense or controls the vertical deflection plate 42 of the cathode ray tube 44.

The output from input signal source 19' is fed to a gating and matrixing circuit 4S whose output is used to control amplifier 4S which controls the strength or intensity of the electron beam of cathode ray tube 44. The output H of the signal source 10 is fed specifically into a voltage divider chain of resistors 46a through 46d and 47.

Between input signal 1t? and resistor 46d is tap Stia; between resistors 46d and 46c is tap 56h; between resistors 46c and 46h is tap Stic; between resistors 46h and 46a is tap 56d; between resistors 46a and ground resistor 47 is tap 56e. The output from taps 56e, Stia', 5de, iib, and 56a is fed respectively to Schmitt trigger circuits 52a to 52e respectively. The output from the l tap of Schmitt trigger circuits 52a through 52e is illustrated as waveforms I, I, K, L and M of FIG. 2. The outputs from the tap of Schmitt trigger circuits 52a through 52d are the inverse or waveforms of I, J, K and L.

Also shown in the gating and matrixing circuit 45 are and gates 54, 56, S, 60 and 62. Also in conjunction with these and gates are or gates 64 and 66. An or gate will have an output level whenever a signal is present on any or all of its inputs. Circuit means are provided connecting output E of fiip-op 22 and the output H of Schmitt trigger circuit 52a to the input of and gate 54. And gate 56 has three input taps. These input taps are connected to the output tap of Schmitt trigger circuit 52a, the output of fiip-f'lop 18 and the l output of Schmitt trigger circuit 52b.

Or gate 64 has connected to its input, the output of fiip-fiop 18 and the output of iiip-fiop 22 of the counting circuit. And gate 58 has connected thereto the output of or gate 64, the output from the 0 tap of Schmitt trigger circuit 52!) and the output from the l tap of Schmitt trigger circuit 52e. Or gate 66 has connected thereto the output of each of the fiip-ops 18, and 22 of the ring counter 16. And gate 60 has connected thereto the output of or gate 66, the output from the O tap of Schmitt trigger circuit 52C and the output from the l tap of Schmitt trigger circuit 52d.

The output of and circuit 54, and circuit 56, and circuit 5S, and circuit 60, and and circuit 62 are provided respectively with resistors 64, 66, 68, 70 and 72. These resistors together with ground resistor 73 provide a mixing network or matrix for combining all outputs onto one line as at junction 74. The signal from junction 74, which is represented by waveform N of FIG. 2, for example, is connected to amplifier 48. The output of amplifier 4S controls the intensity of electron beam gun 76. Gun 76 is provided with a bias resistor 78.

The sawtooth waveform from sweep generator 12 is fed to horizontal defiection amplifier 82. The output of horizontal defiection ampliiier 82 is applied to the horizontal deflection plates Si? of cathode ray tube 44.

The face of cathode ray tube 44 is divided into three bands, 84, 36 and S8. Each band is coated with a material which emits light of one of the three primary colors when struck by electrons. Preferably the materials are three different phosphors. One band 84 is such as to emit red, the middle band 86 emits blue, and the lower band SS emits green. Positioned in front, and spaced from, the face of cathode ray tube 44 is recording drum 92 upon which is mounted a color-sensitive recording medium 94. Spaced between the face of the cathode ray tube 44 and the recording medium 94 is lens 90 which is a cylindrical columnating lens capable of focusing the light from the cathode ray tube face into a single line of light on the photographic film 94. In other words, no matter which of the bands, red, blue or green, upon which the light is being emitted from the cathode ray tube, the light will pass through lens 941 and fall upon the same line on recording medium 94.

Having described the structural components of the embodiment of FIG. l, attention will now be directed briefly toward a discussion of its operation. For convenience in this discussion a true signal is one which is negative relative to ground during the on state, and an untrue signal is negative relative to ground during the ofi state. This will apply especially to the ip-fiops 18, 20 and 22, (comprising a ring counter 16), and to Schmitt trigger circuits 52a through 52d. The l Output is the true output, and the O output is the untrue output. In the digital art this is known as negative logic, and is widely used because of its ease of construction with semiconductor devices.

Sweep generator 12 is selected to have a relatively high frequency sawtooth waveform having fast retrace and linear sweep. Such a waveform is illustrated as waveform A in FIG. 2. The output of sweep generator 12 is amplified by amplifier 82 and is applied to the horizontal deflection plates Sti of cathode ray tube 44 to provide horizontal sweeping of the electron beam across the tube face.

The sawtooth waveform output from sweep generator 2 is also applied to trigger pulse Shaper 14 which forms sharp spikes coincident with the retrace of the sweep. These spikes are illustrated in the waveform B of FIG. 2. rThese spikes are applied to the three and gates, 24, 26 and 28. Only one of the multivibrators 18, 20 and 22 can be on at one time. Assume that multivibrator 18 is the one that is on-this enables and gate 26 to the right of the multivibrator so that the next trigger pulse from trigger pulse Shaper 14 can turn the next multivibrator 20 on. At the same time the gated pulse is fed back to the reset of the first multivibrator 1 8 to turn it ofi Multivibrator 22 is unaffected because its gate 28 was not enabled by an on signal from multivibrator 20. This same sequence of events causes each multivibrator 13, 20 and 22 in turn and in sequence to be in the on condition. Since multivibrator 18 is connected to multivibrator 22 in the same way that multivibrator 20 is connected to 18, and is also connected in the same manner as multivibrator 22 is connected to multivibrator 20, a ring counter circuit 16 is obtained. This particular circuit can also be called a tri-stable switch.

The output signal from multivibrator 18 is added to the inverted output from multivibrator 22 in resistor 37 through isolating resistors 39 and 32 and D.C. isolating or blocking capacitors 36 and 38. This results in a repeating stair-step waveform as shown in waveform G of FIG. 2. This stair-step waveform G is amplified in amplifier 40 and the amplified signal is connected to the vertical deflection plates 42 and the cathode ray tube 44. This vertical defiection, synchronized with the horizontal deflection previously discussed, results in the beam of electrons in the cathode ray tube being swept sequentially and successively across the three different color bands in the manner illustrated in FIG. 3.

The input signal which is desired to be displayed is reproduced or otherwise obtained from input signal source 11i. This signal can be any time-varying signal desired, such as a series of Voltage levels in which each level is proportional to the duration of each half cycle of the original seismic signal. A portion of such a signal is illustrated in curve H of FIG. 2. The input voltage from source 10 is thus fed or applied to a voltage divider resistance 46a through 46d for obtaining different proportions of the input signal to apply to the Schmitt trigger circuits 52a through 52e. These Schmitt trigger circuits can be bi-stable circuits of conventional design which will trigger to the on state whenever the input exceeds some minimum value, and will trigger ofi whenever the input drops below some certain selected value. The true outputs of the Schmitt trigger circuits, that is from the l connections of the Schmitt trigger circuits 52a, 52b, 52C, 52d and 52e, are fed respectively to and gates 54, 56, 58, 6@ and 62. The inverted or untrue signal from the 0 taps of Schmitt trigger circuits 52a,

arcanes 5211, 52e and 52d are fed respectively to and gates 56, 5S, 6@ and 62 respectively. y

The conduits 95, 96, `and 97 from the outputs of the three bi-stable muitivibrators l, 2t) and 22 of ring counter le are labeled ,greem blue and red respectively as each is in its on state when that particular color band is being scanned by the electron beam of cathode ray tube 44. l

The circuitrin FlG. 1 shows one of many possible arrangements of connecting the three color gatingsignals from ring counter le vto the various and and or gates of gating and matrixing circuitlS. In the arrangement of FIG. 1, a voltage will appear .at the output of gate 54 if, and only if, Schmitt trigger circuit 52a is on and bi-stable multivibrator 22 is on vSince tap 59e is nearest ground potential, vSchmitt trigger circuit 52a receives the smallest amplitude signal from the voltage divider formed by resistors 46a through 46d and 47. Thus a much larger signal is required from the input source 1t) to trigger circuit 52a on than for any of the other Schmitt trigger circuits. Assuming each trigger circuit has the same trigger level, Schmitt trigger circuit 52a is the least sensitive, 52b the next least sensitive, and so on, with 52e being most sensitive. If Schmitt trigger circuit 52a is on, then so must all other Schmitt trigger circuits 52h through 52e likewise be on'since their trigger level would have been exceeded before the trigger level of 52a is reached. The inverted output from the O tap of Schmitt trigger circuit 52a inhibits and gate 56 since it is at ground or zero voltage. .Gates 58, dit and 62 are likewise inhibited by outputs of the 0 taps of Schmitt trigger circuits SZb, 52C, and 52d, respectively, since they likewise are at zero voltage. Thus, the grid of the electron gun in the cathode ray tube 4d is in the cut-oit state except when the beam is sweeping across the red-emitting phosphor or band 34. The result is therefore a red color or light being focused on the reproducing film 94 indicated by line 93. The red color on the recording medium represents a selected feature of the input signal; c g. the occurrence of a certain amplitude level.

`ln a similar manner, if Schmitt trigger circuits 52a through 52C are oit but- Schmitt trigger circuits 52d and 52e are on, then gates 54, 56 and 63 will be inhibited by the "'l tap outputs of Schmitt trigger circuits 52a, 52b, and 52C being at ground or zero voltage. Gate 60 therefore isthe only one which is not inhibited from passing a signal. All three color signals 95, 96, and 97 are present on and gate @il through or gate 66, so an output voltage appears because Schmitt trigger circuit 52d is on and the G tap of Schmitt trigger circuit 512e is 011. inverted signal is considered to be on and vice versa.)

fIt will be remembered that only multivibrator 1S or Ztl or 22 is on at any one given time, asillustrated in curves D, E, and F of FIG. 2. The result is that the grid of the electron gun in cathode ray tube dit allows the electron beam to pass to the phosphor screen face during the time it is sweeping across each of the three color phosphors or bands 84, 86, and 88. in such an instance there will then be 'recorded three narrowrstrips, one of green, one of blue and one of red, on the color recording medium 9d. However, since the sweep rate is high, the recording medium will not resolve the three separate colors but will mix them to givewhite. This white color is assigned to represent another feature ofthe input signal, eg. another amplitude level. Other combinations give other colors. Since virtually any color can be obtained by the proper mixture of red, blue and green light, this system is capable of representing features of the input signal in any desired set of colors. The colors are varied depending upon thegating used andthe amount of color signals on conduits 95, 9e, and 97 allowed to pass through the gates.

Resistors 64, 66, 68, 70 and 72 are used to balance the output for diiterent colors. This is used since light is (When Schmitt trigger circuit 52e is oitf the n present on recording medium 94 for only one-third of the time when producing one of the primary colors, twothirds of the time for equal addition of two primaries, and all the time for three-color (or white) mixture.

lf it is desired to achieve different hues than the primaries or complements and white, then various additional resistances can be added between the connecting conduits 95, 96 and 97 and the or gates 64 and 66. Further,

as many gates and associated trigger circuits can be used as desired so that any number of desired color separations can be obtained.

It will be noted that the foregoing description has been concerned primarily with merely one preferred structure of the embodiment of the invention. It will be apparent that numerous modications and variations may be incorporated in the system without departing from the spirit or scope of the invention. In particular, it is evident that the use of negative logic has been used herein only for purposes of illustrating one embodiment of the invention. Positive logic can also be used equally well.

What is claimed is:

l. A system for presenting a signal having amplitude variations and in which system a cathode ray tube is used, the improvement which comprises: three distinct bands of material on the face of said cathode ray tube, each band emitting a separate primary color when energized by the electron beam from the electron gun of said cathode ray tube; means to sweep traversely the beam successively across each band; a recording medium; means to control the energizing of the electron gun during each sweep according to the amplitude of the signal being processed; means to move said recording medium normal with respect to the sweep across the face of said cathode ray tube; and opt-ical means of a character to display the beam of light received from the cathode ray tube as a single line upon said recording medium.

2. A system tor presenting a signal having amplitude variations which comprises in combination: a cathode ray tube having horizontal denection plates and vertical deflection plates, the face of said cathode ray tube being coated with three bands of material, the irst band emitting a red light, the second a blue light, and the third a green light when energized .by an electron beam; a sawtooth generator; means connecting the output of said sawtooth generator to the horizontal deflection plates of said cathode ray tube; control means -to activate said vertical deflection plates so as to move the electron beam 'from one band on the face of the cathode ray tube to the Vnext at each peak of the sawtooth waveform of the output of said sawtooth generator; energizing means to energize'fully said electron beam during each sweep for its entire duration upon the occurrence of selected amplitude llevels of said signal assigned for that sweep; a recording medium; means to move said recording medium normal with respect to the sweep across the face of said cathode ray tube; and optical means of a character for focusing the beam of light received from the cathode ray tube as a single line upon said recording medium.

3. A system for presenting a signal having amplitude variations which comprises: a cathode ray tube `having horizontal deflection plates and vertical deflection plates, the face of said cathode ray tube having three distinct bands of material, each band emitting a separate primary color when energized by the electron beam in said cathode ray tube; a sawtooth generator; means connecting the horizontal deilection plates of said cathode ray tube with said sawtooth generator; means connected to said vertical plates to move the electron beam successively from one bandl to the other at each peak of the output signal from said sawtooth generator; means to energize said electron gunrduring each sweep upon the occurrence of a selected feature of the signal during that sweep; a recording medium; means to move said recording medium normal with respect to the horizontal axis of the face of said cathode ray tube; and optical means of a character to display the beam of light received from the cathode ray tube as a single line upon said recording medium.

4. A system for presenting a signal having amplitude variations which comprises: a cathode ray tube having an electron gun and also having horizontal deflection plates vertical dellection pla-tes, the fa-ce of said cathode ray tube having three distinct bands of material, one band emitting a red color, a second band emitting a blue color, tand a third band emitting a green color upon energization by an electron beam from said electron gun in said cathode .ray tube; a sawtooth generator; means connecting the horizontal deflection plates of said cathode ray tube with said sawtooth generator; control means to move the electron `beam sequentially from one band to the other at each re-l trace of the waveform from the sawtooth generator; a gating and matrixing circuit electrically connected to receive the signal lbeing processed and whose output is electrically connected to the gun of said cathode ray tube and of a character to control the energization of the electron gun with said cathode ray tube for each sweep of the electron beam as a function of assigned amplitude intervals of the signal; a photo-sensitive recording medium; means to move said recording medium with respect to the face of said cathode ray tube; and means of `a character to display the beam of light received from the cathode ray tube las -a single relatively straight line upon said recording medium for each horizontal sweep during which the electron gun is energized.

5. A system for presenting a seismic signal having amplitude variation and in which system a cathode ray tube is used, the improvement which comprises:

three distinct bands of material on the face of said cathode ray tube, each band emitting a separate color when energized by an electron beam from the electron gun of said cathode ray tube;

a sawtooth generator;

means to sweep traversely the'be-am across the face of said tube in accordance with the output of said sawtooth generator;

a voltage divider having an input and a plurality of contact points thereon;

means to connect the seismic signal to the input of said voltage divider;

control means including a ring counter electrically connected to the output of said sawtooth generator and whose output is a series of repeating sequential stepped waveforms having three levels of equal duration, each such level being for a period coincident with the sweep of said sawtooth generator, the output of said ring counter being connected to the vertical deflection plates of said cathode ray tube;

means fully energizing the electron gun of said cathode ray tube for the complete duration of a sweep upon the simultaneous occurrence of a voltage level from said ring counter and a voltage appearing at a contact on said voltage divider assigned to such voltage level.

6. An apparatus as deined in claim 5 including a recording medium; means to move said recording medium normal with respect to the sweep across the face of said cathode ray tube; and optical means to display the beam of light received from the cathode ray tube as a single relatively straight line upon said recording medium.

7. A system for presenting a signal having an amplitude variation which comprises:

a cathode ray tube having horizontal deflection plates and vertical deection plates, the face of said cathode ray tube being coated with three bands of material, the first band emitting a first color light, the second band a second color light, and the third band a third color light when energized by an electron beam;

a sawtooth generator;

means connecting the output of said sawtooth generator to the horizontal deflection plates of said cathode ray tube;

energizing means to energize said electron beam during each sweep for its entire duration on the occurrence of selected amplitude levels of said signal assigned for that sweep; and

control means to activate said vertical deflection plates so as to move the electron beam from one band on the face of the cathode ray tube to the next at each peak of the sawtooth waveform of the output of said sawtooth generator, said control means including a ring counter having three hip-hops and being electrically connected to the output of said sawtooth generatoi` and whose output is a series of reepating sequentially stepped waveforms having three levels of equal duration, each such level being for a period coincident with the sweep of said sawtooth generator, the "1 output of each said iiip-tlop enabling the energizing means upon the simultaneous occurrence of such "1 output and the occurrence of its associated selected amplitude level of said signal.

References Cited by the Examiner UNiTED STATES PATENTS 12/43 Du Mont et al l78-5.4 3/62 Walker 346-110 OTHER REFERENCES LEYLAND M. MARTIN, Primary Examiner.

LEG SMILOW, Examiner. 

1. A SYSTEM FOR PRESENTING A SIGNAL HAVING AMPLITUDE VARIATIONS AND IN WHICH SYSTEM A CATHODE RAY TUBE IS USED, THE IMPROVEMENT WHICH COMPRISES: THREE DISTINCT BANDS OF MATERIAL ON THE FACE OF SAID CATHODE RAY TUBE, EACH BAND EMITTING A SEPARATE PRIMARY COLOR WHEN ENERGIZED BY THE ELECTRON BEAM FROM THE ELECTRON GUN OF SAID CATHODE RAY TUBE; MEANS TO SWEEP TRAVERSELY THE BEAM SUCCESSIVELY ACROSS EACH BAND; A RECORDING MEDIUM; MEANS TO CONTROL THE ENERGIZING OF THE ELECTRON GUN DURING EACH SWEEP ACCORDING TO THE AMPLITUDE OF THE SIGNAL BEING PROCESSED; MEANS TO MOVE SAID RECORDING MEDIUM NORMAL WITH RESPECT TO THE SWEEP ACROSS THE FACE OF SAID CATHODE RAY TUBE; AND OPTICAL MEANS OF A CHARACTER TO DISPLAY THE BEAM OF LIGHT RECEIVED FROM THE CATHODE RAY TUBE AS A SINGLE LINE UPON SAID RECORDING MEDIUM. 